My coolant temp guage does not work at all, just sits there. I am trying to order a replacement from rock-auto.com. They have a coolant temperature sensor AND a coolant temperature sender, both of which look identical. One is around $10 bucks, the other is $40. I know that one goes directly to the gauge from the driver's side of the head, and the other one goes to the engine's computer. Which one do I need for a dead gauge?

 

This the sensor near the fuel filter



This is the temp sensor at the back of the head



Which is the PCM sensor and which is the guage sender?

 

PCM sensor is near the filter, it is only on automatic trucks.

 

The coolant temperature sensor is located at the head near the thermostat. It controls when the engine enters closed loop and turning on the radiator fan.

 

We don't have a "Closed Loop" system nor an electrically controlled fan.

And the temperature sensor for the Gauge is located at the rear of the head as is shown above.

These are the 1st gen Cummins diesel engines (Bosch rotary VE injection pump).

 

So what is the plug near the fuel filter for?

 

It tells the PCM when the engine is warm and it can then engage overdrive.